Electric oven



L. w. WILD ELECTRI C OVEN Jan. 1, 1935;

Filed Nov. 2, 1953 Patented Jan. 1, 1935 amcrmc OVEN I Lancelot WilliamWild, London, England, assignor to Wild-Barfield Electric FurnacesLimited. London, England, a British company Application November 2,1933, Serial No. 696,418 In Great Britain November 11, 1932 1 Claim.(o1. sis-3's) This invention relates to electric ovens. Forms of ovenhave already been employed in which a circulating fan of. thecentrifugal type collects. the air within the oven axially and projectsit horizontally outwards against the walls of the oven. By using anappropriate fan it was found that-a whirling action could be given tothe air'which is thus (assuming that the fan is below the work) causedtorise with substantial turbulence effect in whirls past the heaters andit then descends still with considerable turbulence through the workcontained in a suitable con- I tainer or basket preferably the fan.

It has now been found that still further increased efllciency isobtainable by using certain specific arrangements in connection with thefan. Broadly the object of the invention is to provide sucharrangements, the nature of which and the further more specific objectsof the invention 'will'appear from the subsequent description. Inparticular it seems that undesirable turbulence effects can be avoidedand the desired tubulence throughthe work increased by using a revolvingplate immediately adjacent to the edges of the fan blades while stillleaving the delivery free in all directions radially. It is also foundadvantageous to place a guiding ring between the basket or the likecontaining'the work and the fan delivery, this ring extending from thebasket close to the fan blades: it is preferably coned to restrict thefan inlet to a circle of approximately one half of the full diameter ofthe fan and may terminate in a flat plate lying close to and extendingpreferably beyond the edges of the blades; the central portions of theblades may be tapered towards the center away from the cone and theblades themselves preferably hat and radial and may be two or more innumber and of substantial diameter (preferably almost the full diameterof the basket) bringing their edges relatively close to the oven walls.

The invention is illustrated by the accompanying drawing in which Figure1 is a sectional elevation, and

Figure 2 is a horizontal section through the oven just above the fan.

The oven 1 as shown is of cylindrical shape provided with a heatresisting lining and a cover 2. The electrical heating elements 3 aredisposed at intervals near the periphery of the oven and a basket 4provided with a perforated bottom 5 contains the, work. An outercylinder 6 prevents immediately above 'and one below the basket. Whenthese indicate ,work into the annular space containing the heatdirectradiationof heat on to the work, and ensures that heating thereof shalltake place by convection due to the movement of the air.

The basket 4 and outer cylinder 6 are supported by means of columns 7and the fan 10, 10a is 5 disposed at the bottom of the oven.

A ring 9 shaped as a frustrum of a cone extends over substantially thewhole bottom of the basket and terminates at its lower end in the flatplate 8 which extends out beyond the columns 10 7 and leaves an inletopening tothe fan of approximately half the full diameter of the latter.The fan has its radial blades 10a rising from a bottom plate 10. Thecombination of the ring and the bottom plate very largely prevents re-15 turn currents and loss of efficiency. The central portions of theblades are tapered down towards the bottom at 11 to meet the centralboss of the fan and to facilitate the entry of and centrifugal actionupon-the air entering the fan.

As shown the fan is driven by an electric motor 12 and a stufling box 13is provided packed with asbestos or other suitable material. A copper orother good heat conducting disc 14 outside the furnace is arranged uponthe motor as shaft so as to dissipate heat coming down the shaft fromthe oven and prevent it from aifecting the motor or its Two thermocouples 15, 16 are shown one above 30 the same temperature it gives anindication that this is also the temperature of the work since thecirculating air is no longer losing heat in, its passage past the workin the basket.

I claim:-

In a furnace, the combination of a basket containing the work and havinga reticulated floor, a fan drawing air through the basket, the fancomprising a revolving disc remote from the basket and blades fixedthereto, a duct covering substantially the whole area of the basket-andleading to a restricted area at the center of the fan, a fixed plate atthe end of the duct adjacent to the fan extending out to substantiallythe full diameter of the fan, an outer cylinder surrounding the basket,heating elements in an annular space surrounding the outer cylinder, thedelivery of the fan being substantially free in all directions todeliver the air drawn through the ing elements and thence to theopposite end of the basket.

LANCELOT WILLIAM WILD.

